The invention relates to a method for the manufacture of integrated MOS field effect transistor circuits in silicon gate technology wherein the diffused zones are rendered low-impedance by means of a layer consisting of metal silicides having a high melting point; hence the layers are useful as printed conductors. After completion of a polysilicon plane and the production of regions of the circuit serving as source/drain zones, the metal silicide is produced through direct deposition on the semiconductor substrate provided with the MOS structures.
A reduction of the structure sizes of integrated MOS circuits also requires a reduction of the depth of diffusion zones. Accordingly, the layer resistance becomes considerably increased. This leads to undesirably high delay times in the case of n.sup.+ -silicon conductors, and to high source/drain-series resistances which impair the function of short channel transistors.
These difficulties can be avoided through a self-adjusting silicidation of diffusion zones. There is the possibility, in the same method step, of also providing the polysilicon gates with silicide (polycide-gate). From an article by T. Shibata et al from the Proceedings of IEDM 81, paper No. 28.2, page 647 to 650, incorporated herein by reference, it is known to employ platinum silicide for this purpose, which is produced through reaction of a vapor-deposited platinum and a silicon substrate. The disadvantages of this method are:
(a) a consumption of substrate silicon during the silicidation, as a consequence of which a short-circuit danger exists to the substrate given flat diffusion zones;
(b) the temperature stability is guaranteed only for temperatures smaller than 800.degree. C.;
(c) a costly metallization system with a diffusion barrier is necessary; multiple layer etching problems arise; and
(d) the process is not compatible with hydrofluoric acid-containing chemicals.
The short-circuit danger can be avoided through deposition of platinum/silicon mixtures or platinum/tungsten mixtures. Accordingly, in the case of platinum/tungsten, only at the low temperatures the consumption of substrate--silicon is reduced. However, self-adjustment is lost and photolithography steps become necessary.
As self-adjusting alternatives, also a selective tungsten deposition (see P. A. Gargini, J. Beinglass, Proceedings of IEDM 81, Paper No. 3.2, page 54), incorporated herein by reference, was also proposed. Consecutive or following processes, however, are restricted to less than 500.degree. C. since otherwise tungsten silicide formation with silicon consumption in the contact occurs. In the case of flat diffusion zones, this again has, as a consequence, the possibility of substrate short-circuits.